The Loyalton mule deer (Odocoileus hemionus) herd winters west and northwest of Reno, Nevada along the California-Nevada border, extending into the Peterson Mountains, east of Highway 395 in Nevada. A portion of the herd also winters north of I-80 on Peavine Mountain in Nevada. This population represents an interstate migratory herd but also contains year-round residents in both states. Deer migrate southwest into the Sierra Nevada Mountains of California on both sides of Highway 89 from Truckee to Sierraville, mostly staying north of I-80 and into the Tahoe National Forest. Significant challenges include urban development, vehicle collisions on Highways 89, 395, and I80, and large-scale wildfires that have burned winter ranges in both states. Three Highway 89 wildlife crossing structures were installed by California Department of Transportation and the Highway 89 Stewardship Team at Kyburz Flats and two at Sagehen Summit to mitigate impacts from vehicle collisions. These data provide the location of migration routes for mule deer in the Loyalton population in California and Nevada. They were developed from 76 migration sequences collected from a sample size of 31 animals comprising GPS locations collected every 1-3 hours.